Epitaxy, epitaxial growth, and epitaxial deposition refer to growth or deposition of a crystalline layer on a crystalline substrate. The crystalline layer is referred to as an epitaxial layer. The crystalline substrate acts as a template and determines the orientation and lattice constant of the crystalline layer. The crystalline layer can be, in some examples, lattice matched or lattice coincident. A lattice matched crystalline layer can have the same or a very similar lattice constant as the top surface of the crystalline substrate. Lattice matched layers are advantageous between semiconductor materials because they allow for a region of band gap change to be formed in material without introducing a change in crystal structure. This allows construction of devices such as light-emitting diodes, transistors, and radio frequency filters.
Pnictides is the name given to alloys formed from a rare-earth and a group V element such as N, As or P. Some previous uses of pnictides in buffers include GaN grown on ScN buffers due to the relatively small lattice mismatch between these two nitride alloys. Another previously reported example is the use of ErAs in GaAs based device structures (such as solar cells) as tunnel junctions due its semi metallic behavior. The semi metallic characteristic is an attribute shared by most pnictide alloys. Other pnictides based on a rare earth and nitrogen combination (RE+N), such as GdN have been studied and reported on for their ferromagnetic properties. Each of these examples is very limited in its use to the specific characteristic described.